The Forgotten
by storytellerandartist
Summary: The Underground, a vast kingdom of unknown depth and size. Home to the Monsters since a grand war many years ago, banished by the humans. However there is another race that's been forgotten by both sides. A mission from the future will unite them to an unknown enemy, or doom them all to death. I dont own Undertale or anythingfrom it just the AU and OC's and stuff. Art on tumblr
1. Chapter 1: Time to Remember

"Peace, is such a fragile thing. We had peace of sorts, but those days are long gone. No one remembers who started first. Just that the world had lost its only weapon against _them_. Who are they? Where did they come from? That doesn't matter anymore, at least not right now. All the monsters have gathered, well, the _surviving_ ones anyways. However they are not alone, humans have teamed up with them as well as _The Hidden_ , unified against the darkness in combat.

The theory and goal is to send people back to different points in time. To before _them,_ and give ourselves a chance to survive as a whole. It is unknown if we will succeed but if, on the off chance we do. The only war we will be fighting, is each other. My name is Dr. Anna-May and the year is unknown. This video is recorded and kept on our people for those in the past to someday understand why we did it...in hopes of forgiveness. I..." The video message cuts out, a figure in black stands near a tall mountain.

Sans sighed at his station, lost in thought. Was this just another dream of his? He didn't bother to care at this moment, his dreams often appeared to be similar to his actual life. That is till he woke up right where he last nodded off. The most recent ones was one of the worse ones, it left him on edge to say the least. In the back of his mind there was a familiar buzzing sound, one he hadn't heard since before the dreams and nightmares started.

Closing his eyes he focused on that sound, all too suddenly it vanished leaving him to question if he actually heard it or not. It usually stayed longer to simply pester Sans about remembering, what he was supposed to remember was a mystery to him. It wasn't long before his shift ended so he simply stood up and began walking home, the feeling of being watched being unshakeable.

Unknown to Sans he was definitely being watched, from another plain of existence by someone who had long given up leaving its darkness. He is not alone, the vast space had at least one other being that he knew about. With a heavy soul the being had attempted to once more communicate with the only one that remembers them, only for the window between the plains to be slammed closed on him. If only they would remember, then he could help with the time walkers mission. Everything rides on _The Hidden_ being revealed soon and their history _remembered_.


	2. Chapter 2: Something Unusual

On his way home Sans passed Doggo's post, who was oddly enough fast asleep. This being unusual for him, even within the dreams/nightmares. Sans gently shook his shoulder in an attempt to wake him.

"uh, doggo? you ok there pal?"

After getting no response he tried again, this time being more forceful.

"doggo? hey pal this isn't funny wake up!"

Pulling out his phone Sans called Undyne, a friend, co-worker, and Captain of the Royal Guard.

"Hey this is Undyne, CAPTAIN of the Royal Guard, what's your trouble punk?" answered the loud and enthusiastic fish woman.

"undyne its me, sans, listen i'm at doggo's post but he's not waking up or nothing!"

"WHAT DO YOU MEAN HE'S ASLEEP AT HIS POST?!"

"just get over here will ya?!" Sans hangs up and tries to wake doggo again while waiting for Undyne.

After about 30 minutes Undyne finally showed up looking quite angry. Her first course of action was to shout angrily at Doggo, however when that failed she tried shaking him vigorously out of worry.

"What in the world?! Why isn't he waking up?!" She said in a panic while turning to face Sans.

He shrugs in reply, baffled about this strange behaviour from his fellow sentry. Undyne called for medical support for assistance. By the time they had arrived to take Doggo away Papyrus had made his way over, clearly agitated and worried.

"BROTHER YOU ARE LATE GETTING HOME! DO YOU HAVE ANY IDEA HOW WORRIED I WAS ABOUT...YOU? WHATS GOING ON? DID SOMETHING HAPPEN?" Undyne explain the situation while Sans stared at the now empty station, something wasn't right, he could feel it _in his bones._


	3. Chapter 3: Trouble in the Ruins

After explaining things and calming down the tall and worried skeleton, Doggo was sent to be looked after by Dr. Alphys due to many already fearing the worst. Things continued as normal more or less, one of the other sentries had taken Doggo's post for the time being. However more monsters started sleeping without waking up and without reason, in some cases dropping down on the spot into slumber.

As the days went by Sans's dreams and nightmares would get more vivid, and more frequent. Eventually, after nearly 2 weeks of this, the door to the ruins opened. At the sight of this Sans panicked and hid behind a tree. Was this just another dream? With how things have been lately he wouldn't be surprised but, didn't he just wake up from a dream at his station? The only way to tell was to just watch the human until they reach his station. No greetings, no warning of his or his over zealous brother, simple observation.

Giving a nod has was drawn from his thoughts by someone giving worried shouts. Taking a peek Sans spotted the source, the human was calling for help. This didn't make any sense and caught Sans off guard. He carefully approached them and was about to talk to them, when they spun around walked into Sans with a small huff. The small human looked up at Sans and froze, fear clear in their eyes.

"uh, hey buddy. you doing ok there? I haven't really seen a hu..." Sans was cut short when the human suddenly started to shake worse then an excited Temmie!

"Y...your the one f...from...I...I...!" Sans eye sockets widened in shock. Did the human know about the dreams? If so then how?

"from what? what do you know kid?" He demanded, the human went slightly pale in the face from fear. A sharp pain in his skull caused Sans to let go and groan.

"P...please you have to help! Th...the lady in the ruins! She wont wake up! I...I've tried everything i could think of!" The human stuttered and shouted obviously worried and afraid. Sans could hardly hear what they were saying. He could feel his eye sockets closing without his permission. The last thing he saw was the human panicking and the sight of a familiar looking bush.


	4. Chapter 4: A Hero is Here

Sans looked around him, he was in the judgement hall, had he teleported? Was what happened at just another dream? Perhaps this was a dream, whatever the answer he was interrupted by his thoughts when he heard footsteps. They were small and light, he knew those steps all too well. However the hallway was soon replaced with utter darkness, this was strange, so many new things were happening and if frightened him. Suddenly the _"floor"_ fell beneath him and was sent plummeting into the unending darkness.

The moment the skeleton started falling over was when the young human started screaming. Why was this happening?! The child wept and ran off, after all if he was real then maybe...aha! They were right, walking up the path was the other skeleton! Never before had they been so thankful for their odd dreams/nightmares, if they were anything to go by this monster was friendly.

"HELP! THERE ARE MONSTERS THAT NEED HELP OVER HERE!" They called hoping that they would be heard. Papyrus was worried and had decided to check on his brother, however when he arrived there was no sign of him! Before he could call out or look for him a faint cry for help reached his non existing ears. Quickly he ran towards the voice, after all a royal guard must help those in need! It wasn't long till he found the source of the shouts, they looked to be a child however he hadn't seen anything like them.

"GREETINGS! I AM THE GREAT PAPYRUS, ARE YOU BY CHANCE A HUMAN?" Not having seen one before he thought he would ask, after all it was his duty to capture humans.

"Please! Th...there's no time to explain! There are monsters that need help, I'm scared and don't know what to do. Please help..." _MONSTERS THAT NEED HELP? THAT SOUNDS LIKE THE PERFECT JOB FOR THE GREAT PAPYRUS!_ After the tall skeleton made a 'heroic' pose they replied "LEAD THE WAY I SHALL ASSIST THEM WITH GREAT EASE!" The child nodded and lead him towards the ruins hurriedly, however as they approached a blue hoody on the ground was spotted. _NO...S...SANS?_


	5. Chapter 5: Unlikely Encounters

It took a while to clear things up with Papyrus but eventually he understood the situation. He had taken Sans into the ruins where the young human waited while he called for help. Tension was high, after all if the dreams were anything to go off of, the other monsters may not be as understanding as the tall skeleton currently pacing the room. Alphys was working in her lab, trying desperately to find a clue as to the cause of whatever phenomenon was happening in the Underground.

Having no clues as to the cause or a way of waking the sleeping monsters without use of her previous experiments, it was decided that she needed a noodle break. Just as she was going to eat however her phone rang startling her. After seeing who's number it was she picked up right away in a panic. Oh please no please no please let this not be what I think it is!

"H...Hello Papyrus! What seems to be the m...matter?" She stuttered, already getting another table ready for examination.

"DR. ALPHYS! PLEASE HURRY TO THE RUINS! S...SANS...HE WONT WAKE UP! THERE IS ALSO A STRANGE CREATURE I HAVEN'T SEE BEFORE AND MONSTER THAT LOOKS TO BE THE MISSING QUEEN!" Said a booming and panicked voice through the phone.

This took her a bit by surprise, could it be the queen was found? What was the strange creature that was with her?

"P...Please calm down I'll send someone over right away!" Before waiting for a response she hung up to dial the royal guard, after all this was an emergency! Everything seemed to be going from bad to worse, with there now being a dozen cases of the mysterious sleeping with no end in sight, many feared the worst.

Something was wrong...very wrong...there was a new presence here, however at the same time they were not here. It was not an easy task navigating the darkness, nor was it difficult. After all having spent how knows how long trapped here would make anyone somewhat accustomed to the way it works.

As the goopy looking monster made its way around it spotted the source. A floating consciousness, a mind separated from the body, how it ended up here was a troubling mystery. They seemed to be looking around quite lost but the figure was one he knew! Approaching carefully he spoke, strange symbols appearing overhead as he did so. "It has been a long time Sans" "gaster?!"


	6. Chapter 6: Freaky Findings

_"It has been a long time Sans, however your presence here is...unorthodox to say the least. I am certain you have many things to ask of me, however it is unwise for your consciousness to remain here for extended periods of time."_

Sans floated there in a stunned silence amongst the darkness, could it really be him, his mentor and father, there were so many questions to ask but only one is vital.

"where's paps?" _"I know not of his whereabouts currently, I only know of our own."_

"thought you said only my consciousness was here, what you couldn't _make up your mind_?" Gaster glared at Sans then burst out into a fit of laughter.

 _"You certainly haven't changed much have you?"_ The two floated there laughing for a few moments before an awkward silence came over them.

"so uh, what are you doing here anyways? where is here exactly?" Sans looked around the darkness, taking a mental note of all the screen like openings appearing and disappearing.

 _"This is a place known as the void. A realm that most can't even see let alone enter. I know of only two living beings in this space, myself and another who I have only seen glimpses of."_

"alright then what are these things?" Sans asks as a screen like shape floats near by, showing a large city.

 _"These screens show various areas where there is life. Through these I have attempted to contact you as well as several humans as well. However these are not where your focus should be."_ Sans turned to Gaster clearly confused and concerned.

Gaster had taken hold of Sans' arm, and quickly moved through the darkness with him in tow. With no definite way of telling how much time had passed they came to a stop, with a sight that left Sans shaking. Right there within the never ending darkness, was the very mountain the monsters where sealed under, inside what appeared to be a bubble of magic.

 _"It appears it is time for you to return to your body, I hope that we can speak again soon."_ Sans sat up in a frantic panting, his eyes darting around...wait...where was he? He had no time to even think as he was soon bombarded with enthusiastic hugs from his brother.

"THANK GOODNESS IT WORKED! I WAS SO WORRIED ABOUT YOU BROTHER!" Papyrus's voice booming in Sans's non-existent ears. Still dazed and severally confused he sat there staring at the wall. What in all creation did he just experience!?


End file.
